224 PRACTICAL ORGANIC CHEMISTRY
weighed in a tube which is of such a length that it rests against
the side of the nitrometer flask. About; 10 c.c. of the reagent are
poured into the flask ; the tube containing the substance, which is
dissolved in a little amyl ether, is slipped in ; the flask is attached
to the side tube of the nitrometer and is then cut off from the
nitrometer tube by turning the tap. A little moisture and
oxygen in the flask are absorbed by the reagent and the pressure
falls. After standing for J hour the nitrometer tube is nearly filled
up with mercury, the tap is withdrawn for a moment to readjust
pressure and the tube then completely filled with mercury. The
tap is now turned so as to establish communication between the
flask and nitrometer tube and the mercury reservoir lowered.
The tube containing the solution of the naphthol is inverted
and shaken. Evolution of methane rapidly occurs and in a
short time the volume remains constant. The volume, tempera-
ture and pressure are read off and the percentage of hydroxyl
Extimph.—O'i2o gram /3-naphthol gave 20 c.c. methane at
20 X 17 X 100 _lo.fr
224O X O'I2O
Calculated for C10H7OH ; OH = irS per cent.
(Tschugaeff, Bcr^ 1902, 35, 3912 ; Hibbert and Sudborough,
Proc. Cheui. Soc., 1903, 19, 285 ; Zerewitinoff, Ber^ 1907, 40,
2023.) See Appendix^ p. 315.
Naphthol Yellow, SO*K| | |NO*
Friedlander, Theerfarbenfabrikation, I, 322, II., 215 ; Cain
and Thorpe, The Synthetic Dyestitffs, p. 226.
20 grms. a-naphthol.
80 „ (45 c.c.) cone, sulphuric acid.
4° 55 (j° c-c-) cone, nitric acid (sp. gr. 1*4).
The mixture of a-naphthol and sulphuric acid is heated for
2 hours to 120° and then dissolved in 120 c.c. water. The solu-